Fruit and Vegetable Bruise Threshold Prediction Using Theory of Elasticity and Tissue Failure Properties (With support from USDA-NRICGP)

Determining bruise threshold (drop height at which bruising just begins) from tissue failure properties and whole specimen mass and shape has the advantages of speed and the ability to predict threshold change from failure property changes. Conditioning in turn can influence failure properties; with the result that bruise threshold can be controlled to some degree by commodity conditioning. This work compared bruise threshold prediction using theory of elasticity, tissue failure stress and strain determined by dynamic axial compression (DAC), Poisson’s ratio, and specimen mass and radius of curvature, with results of paired increasing-height multiple-impacting (PIHMI), a whole specimen technique that has proven reliable for determining bruise threshold in apples. The results show that DAC prediction agreed with PIHMI results with a standard error of 1.7 mm for bruise thresholds up to 16 mm.Grouped by hydration level, DAC and PIHMI bruise thresholds were not significantly different (p>0.05) using a paired t-test.